Breeding
Genetics, pollination, selection, stabilisation, seed production.
Backcrossing, IBLs and stabilisation
A backcross crosses offspring back to one parent (the recurrent parent) to recover that parent's genome while keeping a trait from the other: each backcross halves the donor's share (50%, 25%, 12.5%, 6.25%...). An IBL is a line inbred and selected over many generations until it breeds fairly true. 'Stable' should mean measured uniformity across a grow-out, not a generation count.
Breeder record-keeping and naming ethics
Keep a dated record of every plant, cross, batch and test, linked by permanent IDs, so any seed can be traced to its parents. Name lines honestly: a new, unique name for new genetics, the original name only for the original genetics, clear labels (F2, BX, S1, feminised), and never a famous name on something it isn't. Names are claims; records are the evidence. Sex stability is part of the ethics: cull herm-prone plants, never breed from them, and publish every batch's herm rate.
Breeding autoflowers: getting the trait into a photoperiod line
Because autoflowering is recessive in mapped populations, a photo x auto F1 is all photoperiod. You recover autos in the F2 (about 1 in 4) or by backcrossing the F1 to the auto parent (about 1 in 2). To make an auto version of a photoperiod line, alternate crossing to the photo parent with a generation that reveals autos, or use a DNA marker to keep carriers.
Chemotype inheritance: how THC and CBD synthase alleles pass on
Whether a plant is THC dominant, CBD dominant or mixed is controlled mainly by a single inheritance block carrying THCA synthase and CBDA synthase genes, which behaves close to codominant: THC x CBD gives mixed (type II) F1s and a 1:2:1 split in the F2. CBG-dominant and cannabinoid-free types come from non-functional synthase alleles. Total cannabinoid amount is a separate, quantitative trait.
Clone-only cuts and how to preserve them
A clone-only is one selected genotype kept alive by cuttings. It can be lost to pests, disease, hop latent viroid (HLVd) or accident, and it accumulates rare somatic mutations, which are not the same thing as a loss. Cuts from different parts of a plant can also behave differently (topophysis), so take them from consistent locations. Preserve it with clean, tested mothers in at least two locations, regular fresh cuttings, a tissue-culture backup where possible, and seed (S1s or crosses) as genetic insurance, not as a copy.
Collecting and storing cannabis pollen
Collect pollen from freshly opened sacs in still, clean air, sieve it, dry it briefly, and use it within days, or mix it with a dry carrier (baked flour), seal it with desiccant and freeze it. Cannabis pollen loses viability within about a week in a fridge; one study kept it viable for at least four months by mixing it 1:10 with baked flour, vacuum-drying and storing in liquid nitrogen. Home freezer storage is grower practice and should be germination tested.
F1, F2, F3 explained: what filial generations really mean
An F1 is the first generation from two parents; it is uniform only if both parents were true-breeding (inbred). An F2 comes from crossing F1 siblings and shows the most variation. Each later generation of sib-mating with selection increases uniformity slowly. In cannabis, most 'F1 hybrids' are crosses of heterozygous clones, so they behave like segregating F2s.
Feminised seed and sex reversal: methods, with safety notes
Feminised seed is made by forcing a genetic female to grow male flowers, then using that pollen on another (or the same) female. Silver ions block ethylene action; silver thiosulfate (STS) sprayed at about 3 mM silver was the most effective treatment in a controlled hemp study, and colloidal silver also works. Silver compounds are hazardous: wear gloves and eye protection, never consume treated plants, and dispose of waste as hazardous. Careless feminising (unproven donors, stress-herm pollen) is a main source of herm-prone seed; reverse only females proven stable over at least two runs.
Genotyping: what a DNA test can and can't prove
A DNA test can reliably show whether two samples are the same genotype, rule out a claimed parent (exclusion), support a parent-child relationship when both parents are sampled, predict sex and chemotype class from seedlings, and place a plant on a map of genetic groups. It cannot prove a 40-year-old pedigree from a name, measure THC %, tell you a plant's 'indica percentage', or guarantee how it will grow.
How to document lineage evidence (GB-ID evidence levels L0-L4)
On GenetixBay every parentage statement is a claim with an evidence level: L0 unverified, L1 community reported with a source, L2 breeder reported, L3 documented by an accepted GB-DOC, L4 lab-confirmed by a genomic report consistent with the parent-child relationship. Breeders raise the level by attaching dated, original evidence and, where possible, by recording crosses on the platform as they happen.
Inbreeding depression and hybrid vigour
Inbreeding makes hidden harmful recessive alleles homozygous, so inbred plants often lose vigour, yield and fertility (inbreeding depression). Crossing unrelated lines masks those alleles and can push F1s above both parents (hybrid vigour, or heterosis). The vigour fades in the F2 because the masking breaks down as genes segregate.
Mendelian genetics for growers, with Punnett squares
Traits controlled by one gene follow Mendel's rules: each parent passes one of its two alleles at random, so a cross of two heterozygotes gives a 1:2:1 genotype ratio and, for a dominant trait, a 3:1 look. In cannabis the clearest single-gene examples are autoflowering (recessive) and the THC/CBD chemotype switch (close to codominant).
Pollination and seed production, step by step
Pollinate females about 2-4 weeks into flower when stigmas are white and receptive, using fresh or stored pollen applied with a brush or bag to marked branches; seeds mature in roughly 5-7 weeks. Isolation is everything: pollen travels on air, clothing and fans, so a planned cross needs a separate space or strict bagging, and every pollination gets a dated record.
Polyhybrids vs landraces: what each gives a breeder
A landrace is a locally adapted, farmer-maintained population with a regional history; it is variable but coherent, and a reservoir of diversity. A polyhybrid is a modern line with many ancestors from different gene pools; it can be highly productive but is heterozygous and segregates unpredictably. Breeders use landraces as sources of new traits and polyhybrids as elite starting material.
Quantitative traits and heritability: why most good traits are hard to fix
Yield, potency, terpene totals, vigour and flowering time are controlled by many genes plus environment. Heritability (the share of variation due to genes in a given population and setting) predicts how much of a selected plant's advantage passes to its offspring: response = heritability x selection differential. Cannabinoid ratios are highly heritable; absolute THC % and yield much less so.
S1s and selfing: what happens when a plant pollinates itself
An S1 is seed from a plant pollinated by its own pollen, usually by reversing one female clone or branch. S1s are feminised, and they are not copies of the parent: each S1 seed is a new genotype. Selfing halves heterozygosity per generation, reveals hidden recessives (good and bad), and is a fast way to test what a clone carries. Done carelessly, especially S1 on S1 from plants that herm, it is one of the main ways herm-prone lines are made; only self proven-stable females and cull every intersex offspring.
Seed germination testing and quality control for breeders
Before seed leaves your hands, test it: germinate a random sample of at least 100 seeds (400 in four replicates is the lab standard) and count normal seedlings, not just cracked seeds. Report the result with the date on the batch record. Store seed cool and dry; one study recommended about 5 °C to keep germination for years.
Selection and pheno hunting: sample sizes and scoring rubrics
A pheno hunt is a selection experiment: grow enough seeds to have a real chance of finding what you want, clone every candidate before flowering, score each plant on a fixed weighted rubric, and re-grow the top few as clones before you call a keeper. The plants needed follow 1 - (1 - p)^n: a 1-in-10 type needs 29 plants for a 95% chance of seeing at least one. Sex stability is a gate: any plant that herms is culled, whatever else it scores.
Tissue culture basics for cannabis growers and breeders
Tissue culture grows small pieces of a plant (usually nodes or shoot tips) on a sterile gel medium, giving clean, compact, long-lived backups of clones and a route to cleaning up infected stock. Cannabis tissue culture works but is genotype dependent and poorly replicated in the literature; contamination control is the main skill.
